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| author |   Paolo Bonzini <pbonzini@redhat.com> | 2019-11-04 13:23:53 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-11-11 15:48:03 +0100 |
| commit | e2d3fcaf939dded3da604a25ebbea9fb954c2280 (patch) | |
| tree | 85f53e7f8e4fc845cf162cd4fda4dcb8d6e6207c | |
| parent | KVM: Fix NULL-ptr deref after kvm_create_vm fails (diff) | |
| download | linux-dev-e2d3fcaf939dded3da604a25ebbea9fb954c2280.tar.xz linux-dev-e2d3fcaf939dded3da604a25ebbea9fb954c2280.zip | |
KVM: fix placement of refcount initialization
Reported by syzkaller:
=============================
WARNING: suspicious RCU usage
-----------------------------
./include/linux/kvm_host.h:536 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
no locks held by repro_11/12688.
stack backtrace:
Call Trace:
dump_stack+0x7d/0xc5
lockdep_rcu_suspicious+0x123/0x170
kvm_dev_ioctl+0x9a9/0x1260 [kvm]
do_vfs_ioctl+0x1a1/0xfb0
ksys_ioctl+0x6d/0x80
__x64_sys_ioctl+0x73/0xb0
do_syscall_64+0x108/0xaa0
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Commit a97b0e773e4 (kvm: call kvm_arch_destroy_vm if vm creation fails)
sets users_count to 1 before kvm_arch_init_vm(), however, if kvm_arch_init_vm()
fails, we need to decrease this count. By moving it earlier, we can push
the decrease to out_err_no_arch_destroy_vm without introducing yet another
error label.
syzkaller source: https://syzkaller.appspot.com/x/repro.c?x=15209b84e00000
Reported-by: syzbot+75475908cd0910f141ee@syzkaller.appspotmail.com
Fixes: a97b0e773e49 ("kvm: call kvm_arch_destroy_vm if vm creation fails")
Cc: Jim Mattson <jmattson@google.com>
Analyzed-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | virt/kvm/kvm_main.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index e22ff63e5b1a..e7a07132cd7f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -650,6 +650,7 @@ static struct kvm *kvm_create_vm(unsigned long type) if (init_srcu_struct(&kvm->irq_srcu)) goto out_err_no_irq_srcu; + refcount_set(&kvm->users_count, 1); for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { struct kvm_memslots *slots = kvm_alloc_memslots(); @@ -667,7 +668,6 @@ static struct kvm *kvm_create_vm(unsigned long type) goto out_err_no_arch_destroy_vm; } - refcount_set(&kvm->users_count, 1); r = kvm_arch_init_vm(kvm, type); if (r) goto out_err_no_arch_destroy_vm; @@ -696,8 +696,8 @@ out_err: hardware_disable_all(); out_err_no_disable: kvm_arch_destroy_vm(kvm); - WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count)); out_err_no_arch_destroy_vm: + WARN_ON_ONCE(!refcount_dec_and_test(&kvm->users_count)); for (i = 0; i < KVM_NR_BUSES; i++) kfree(kvm_get_bus(kvm, i)); for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) |